This invention relates to a centrifuge in which the so-called angle rotor carrying a sample is driven at high speed for sedimentation, separation or the like of the sample, and more particularly to a centrifuge cooling arrangement which is designed so that air is drawn into a centrifuge from the outside and directed around a rotor to cool it.
In a centrifuge, a rotor carrying a sample is driven at high speed for separation, sedimentation or the like of the sample. The high-speed revolution of the rotor causes heat generation by friction between the rotor and air to heat the former; and this may in some cases lead to a temperature rise of the sample to decompose it and exert a bad influence on the analysis of the sample. To avoid this, the rotor must be cooled.
In the case of employing the so-called angle rotor, since it takes the form of a truncated cone and has a relatively large peripheral surface area, air on its peripheral surface is blown off downwardly by the rotation of the rotor, causing a decrease in the air pressure in the vicinity of the center of rotation of the rotor on the top thereof. With the provision of an air inlet in a lid of the centrifuge adjacent the center of rotation of the rotor on the top thereof, air is drawn from the outside through the inlet to flow down on the peripheral surface of the rotor while absorbing therefrom heat to cool it. The heat absorbing air is released to the outside from an outer casing of the centrifuge. In the prior art, the rotor is cooled by such a method utilizing the phenomenon caused the rotation of the rotor. With such a cooling arrangement, the rotor can be easily cooled without the necessity of providing a cooling device separately of the centrifuge, and consequently the centrifuge itself can be made small and inexpensive.
In the above centrifuge, however, sample tubes are mounted in the rotor to extend along its peripheral surface and radially of its center of rotation, with the upper end portions of the sample tubes slightly projecting out of the top of the rotor and left open; that is, the upper open ends of the sample tubes lie adjacent the aforesaid air inlet made in the lid. Consequently, floating matter or dust in the air flowing through the air inlet may in some cases get mixed into the sample to exert a bad influence thereon, introducing inaccuracy in the result of inspection.
The sample tubes may also be capped to prevent such floating matter from mixing into the sample, but it is very troublesome to attach a cap to each sample tube and the cap is very likely to be blown off by centrifugal force because of the high-speed revolution of the rotor; therefore, the sample tubes are usually left open. Further, since the upper open end portions of the sample tubes project out of the top of the rotor, as referred to above, the projecting portions of the sample tubes disturb the air stream from the air inlet to prevent the air from smoothly flowing down the peripheral surface of the rotor; turbulence is produced in the air flow to make harsh noises. Further, the turbulent flow of air lowers the air drawing efficiency.
An object of this invention is to provide a cooling structure for centrifuges of the type employing an angle rotor and cooling it by drawing air from the outside which is designed so that even if sample tubes are not capped while in use, floating matter in air hardly gets mixed in a sample to ensure an accurate inspection of the sample.
Another object of this invention is to provide a cooling structure for centrifuges of the type employing an angle rotor and cooling it by automatically drawing air from the outside which is designed so that an air flow drawn from the outside is not disturbed by sample tubes and flows smoothly without swirling, thereby preventing noise generation and providing for enhanced air drawing efficiency.